Aluminum alloys



Patented Oct. 31, 1933 UNITED STATES 1,932,848 ALUMINUM ALLOYS Walter A.Dean and Louis W. Kempf, Cleveland, Ohio, assignors to Aluminum Companyof America, Pittsburgh,

Pennsylvania Pa., a corporation of No Drawing. Application September 21,1932 Serial No. 634,166

2 Claims.

This invention relates to aluminum base alloys containing substantialamounts of magnesium and to the improvement of the properties of thesame. 5 The aluminum base alloys containing 2 to 15 per cent by weightof magnesium are, because of recent developments making them availableas commercial alloys, among the most useful of the aluminum alloys.Their light weight, by reason of their content of magnesium, their highstrength, and their resistance to corrosion have recommended themstrongly as a structural material. In one of the most important uses towhich aluminum base alloys can be put, i. e.,

' as moving parts reciprocating at elevated temperatures, thealuminum-magnesium alloys have been found somewhat deficient in strengthand ductility. It is to the improvement of such properties at elevatedtemperatures (i. e., temperatures of about 400 to 700 Fahrenheit) thatthe present invention is directed.

We have, in the course of an extensive experimentation, discovered thatthe addition of small amounts of antimony and/or bismuth to the aluminumalloys containing 2 to 15 per cent of magnesium will appreciably benefitsuch alloys and, in particular, will tend to maintain a substantial partof the tensile strength and elongation of the alloys when the alloys aresubjected to elevated temperatures. For this purpose, an-

timony and bismuth may be considered as a class of metals although wehave observed that bismuth is to some extent superior. The amount ofantimony and/or bismuth which may be added to the aluminum-magnesiumalloys aforesaid to obtain these results lies within a rather narrowrange. We have discovered that the efiect upon the properties of thealloy is had when amounts of antimony and/or bismuth are addedcorresponding to 0.05 to 0.4 per cent by weight of the total alloy. Butwhen the antimony and/or bismuth content of the alloy exceeds about 0.4per cent by weight of the total alloy,

the effect produced is the reverse and the alloy loses both tensilestrength and ductility, particularly the latter. We have found that theefiect of antimony and bismuth "is particularly pronounced in aluminumbase alloys containing 2 to 8 per cent by Weight of magnesium.

The antimony and bismuth may be used separately' or they may both bepresent in the alloy, but in any case the total amount of these elementsshould not exceed about 0.4 per cent by weight. Aluminum base alloyscontaining 2 to 15 per cent of magnesium and 0.05 to 0.4 per cent ofantimony and/or bismuth in accordance with the principlesof my inventionare considerably improved in their resistance to high temperatures. Forinstance, a sand cast alloy containing 6.0 per cent by weight ofmagnesium, balance 50 principally aluminum, after heating for 4 hours at700 Fahrenheit and then cooled to 600 Fahrenheit, had, when tested atthe latter temperature, a tensile strength of about 14,880 pounds persquare inch and an elongation in 2 inches of about 7.5 per cent. A sandcast alloy of the same composition except that there was present 0.1 percent of antimony had, after the same thermal treatment and at the samefinal temperature, a tensile strength of 15,580 pounds per square inchand an elongation in 2 inches of 9.3 per cent. This example isindicative of the re-v sults obtained by the practice of my inventionwhether antimony or bismuth is the alloying element used. Anotherexample of the beneficial effect of small amounts of antimony and/orbismuth in aluminum-magnesium alloys is shown in the case of a sand castalloy containing 7 per cent magnesium. This alloy had a tensile strengthof 29,700 pounds per square inch, a 0 yield point of 18,000 pounds persquare inch, an elongation of 7.6 per cent in 2 inches, and a Brinellhardness of 66. When to this alloy there was added about 0.2 per cent ofantimony and about 0.12 per cent of bismuth, the tensile strength of thealloy was increased to about 34,- 000 pounds per square inch, the yieldpoint was increased to about 18,200 pounds per square inch, theelongation was increased to 11 per cent in 2 inches, and the hardnesswas increased to 70.

The above-described alloys may be manufactured by any of the well knownmethods such as for instance by melting the aluminum and introducinginto the molten aluminum the proper amounts of the alloying elements insolid form.

The aluminum used in the manufacture of the alloys may be of the highestpurity or itmay contain amounts of usual impurities, and the termaluminum as used herein and in the claims designates the aluminum ofcommerce. It is an incidental property of our alloys that the presenceof iron in amounts as high as 2 per cent by weight is not harmful to thehigh temperature properties of the alloys and, therefore, a wide choicebetween thevarious grades of commercial aluminum is possible.

We claim:

1. A metallic alloy characterized by high physical and tensileproperties at elevated temperatures and consisting of 2.0 to 15.0 percent by 110 weight of magnesium and about0.05 to 0.4 per cent by weightof at least one of the class of elements antimony and bismuth, the totalamount of the antimony and/or bismuth being 5 not greater than 0.4 percent by weight, the

balance being aluminum.

2. A metallic alloy characterized by high physical and tensileproperties at elevated temperatures and consisting of 2.0 to 8.0 percent by

